The present invention relates to an airbag device to protect a vehicle occupant in the event of a collision and the like, and more specifically, relates to an airbag device to be assembled while a folded shape of an airbag is maintained by a shape-maintaining component.
In general, an airbag device serving as a protector for an occupant in a vehicle and the like is configured to include an folded airbag, an inflator to supply gas to the airbag, bag holding components, e.g., a base plate and a case, on which the airbag and the inflator are mounted and fixed, and a cover which is disposed to cover a top surface of the folded airbag and which is torn by an inner pressure of the airbag when the airbag device is actuated.
In such an airbag device, the folded shape of the airbag may be maintained with a shape-maintaining component for the purposes of improving workability in mounting of the above-described cover and of preventing the deformation of the cover due to spontaneous restitution force of the airbag from the folded state during the mounting on a vehicle.
Japanese Patent Publication (Kokai) No. 2000-296746 has disclosed an airbag device including a sheet with a shape of a crank-like long belt serving as the shape-maintaining component, and a folded shape of the airbag has been described in detail in the reference.
FIG. 7 is a sectional view of an airbag device 10 shown in the above-described reference, and FIGS. 8(a) and 8(b) are perspective views showing a state in which an airbag 12 is held with a shape-maintaining component 44.
The airbag device 10 is a driver airbag disposed at a central portion of a steering wheel of an automobile, and is configured to include the airbag 12, an inflator 14, a retainer (referred to as a base plate in the above-described reference) 16, a bag-mounting ring 18, and a module cover 20.
The airbag 12 has a bag shape formed by sewing perimeters of substantially circular two panels (a front panel and a rear panel) with each other, and the rear panel disposed in the inflator 14 side is provided with an opening (mouth portion) 24 for the insertion of the inflator 14 in the central portion.
A mounting flange 14a is provided around the inflator 14, and a gas eject portion is provided on a side perimeter surface of the inflator 14 at a side closer to the front-end than the flange 14a. 
The base plate 16 is composed of a substantially rectangular plate-shaped portion 16a and leg plate portions 16b bending downwardly at an edge of the plate-shaped portion 16a. 
An inflator insertion port 34 is provided at a central portion of the plate-shaped portion 16a of the base plate 16, and the front-end side of the inflator 14 is inserted in the inflator insertion port 34 from the backside, as shown in FIG. 7. The mouth portion 24 of the airbag 12 is mounted and fixed on the perimeter of the inflator insertion port 34 with the mounting rings 18 therebetween.
The mounting ring 18 is a ring-shaped metal component provided with bolts 38 protruding. The bolt 38 is inserted through a bolt through hole 28 provided at a perimeter of the mouth portion 24, and furthermore, is inserted through both a bolt through hole 35 provided in the perimeter of the opening 34 of the base plate 16 and a through hole 14b provided in the flange 14a of the inflator 14, with a nut 39 screwed in.
The leg portions 20a of the module cover 20 are fixed to the leg plate portions 16b with rivets 43, so that the module cover 20 is mounted on the base plate 16.
Reference numeral 44 denotes the shape-maintaining component covering the airbag 12 in a predetermined folded shape in order to maintain the folded shape.
In assembling the airbag device 10, after the airbag 12 is folded as shown in FIGS. 8(a) and 8(b), the bolt 38′ of the mounting ring 18 is inserted through a through hole 44a provided at one end portion of the shape-maintaining component 44. Then, the shape-maintaining component 44 is put over the folded airbag 12, and the bolt 38″ opposite to the above-described bolt 38′ on a diagonal line is inserted through a through hole 44b at the other end portion. In this manner, the shape of the folded airbag 12 is maintained.
The base plate 16 is put over the folded body of the airbag 12, and the bolts 38 are inserted through the bolt through holes 35. The front-end side of the inflator 14 is pushed in the airbag 12 through the opening 34 and the mouth portion 24, and the flange 14a is put on the backside of the base plate 16. At this time, the bolts 38 are inserted through the bolt through holes 14b. The nuts 39 are screwed in the bolts 38. Subsequently, the module cover 20 is put over the folded-airbag portion, and is fixed with rivets 43.
In assembling the airbag device 10, when the module cover 20 is mounted on the base plate 16 while being put over the folded body of the airbag 12, the shape-maintaining component 44 maintains the folded shape of the airbag 12. Consequently, the cover 20 is readily put over the airbag 12 so that the airbag device 10 has excellent workability in assembling. Even after the airbag device 10 is mounted on a vehicle, since the shape-maintaining component 44 maintains the folded shape of the airbag 12, the force caused by the spontaneous restitution of the shape from the folded state can be reduced while the force is applied to the cover 20, thereby preventing the deformation of the cover 20.
When the airbag 12 is inflated by the gas discharged from the inflator 14 in the event of a collision of the vehicle, the shape-maintaining component 44 is torn. The airbag 12 pushes the module cover 20 to open, and is deployed.
As described above, the airbag is folded into the predetermined shape in assembling the airbag device 10. An example of the folding method has been described in detail in Japanese Patent Publication (Kokai) No. 2002-316605.
FIGS. 9(a)–9(f) to 13 are diagrams for illustrating the method of folding an airbag in the above-described reference. An airbag 50 is formed by sewing a front panel 51 and a rear panel 52 with each other, and the rear panel 52 is provided with a gas inlet (mouth portion) 54 and a vent hole 55.
As shown in FIG. 9(a), the front panel 51 of the airbag 50 is allowed to face upward, and the airbag 50 is placed on a flat worktable in a flat shape. In this case, two straight lines intersecting at a center ◯ serves as reference axes X and Y, and specify horizontal and vertical directions.
As shown in FIG. 9(b), an upper part of the airbag 50 is folded along a predetermined first folding line 1a adjacent to the gas inlet 54. As shown in FIGS. 9(c) to 9(e) and 9(f), an end portion of the upper part is rolled along predetermined folding lines 1b, 1c and 1d, toward the front panel side to form an upper deployment portion 61 shown in FIG. 13.
As shown in FIG. 10(a), a right side part is folded over a central part along a predetermined first folding line 4a adjacent to the gas inlet 54. As shown in FIGS. 10(b) to 10(d) and 10(e), an end portion of the right side part is rolled along predetermined folding lines 4b, 4c and 4d toward the front panel side to form a right deployment portion 64 shown in FIG. 13.
As shown in FIG. 11(a), a left side part is folded over the central part along a predetermined first folding line 3a adjacent to the gas inlet 54. As shown in FIGS. 11(b) to 11(d) and 11(e), an end portion of the left side part is rolled along predetermined folding lines 3b, 3c and 3d toward the front panel side to form a left deployment portion 63 shown in FIG. 13.
As shown in FIG. 12(a), a lower side part is folded over the central part along a predetermined first folding line 2a set close to the gas inlet 54. As shown in FIGS. 12(b) to 12(d), an end portion of the lower part is rolled along predetermined folding lines 2b, 2c and 2d toward the occupant side to form a lower deployment portion 62 shown in FIG. 13.
Consequently, as shown in FIG. 13, the right deployment portion 64 and the left deployment portion 63 are overlapped at the occupant side of the folded airbag, and the lower deployment portion 62 is further put over the deployment portions 63 and 64 at the occupant side.
Japanese Patent Publication (Kokai) No. 09-30425 has disclosed that in an airbag device in which only a module cover recedes and a horn switch is turned on so as to sound a horn when a module cover is pushed, a folded airbag is bound to a retainer with a band, and a space for recession of the module cover is formed between the module cover and the top surface of the folded airbag. In this case, the module cover is mounted on the retainer while being movable in a vertical direction (in the direction of approaching or receding from the occupant). An urging device, e.g., a spring, is provided for urging the module cover upwardly.
Airbag devices in which only a module cover recedes and a horn switch is turned on so as to sound a horn when a module cover is pushed have also been disclosed in Japanese Utility Model Publication (Kokai) No. 06-53324, Japanese Utility Model Publication (Kokai) No. 06-53365, and Japanese Utility Model Publication (Kokai) No. 05-92004.
As shown in FIG. 7, Japanese Patent Publication (Kokai) No. 2000-296746 has disclosed the airbag device as if an adequate inner space (clearance) is provided, and the front-end side of the inflator 14 is easily inserted into the airbag 12 through the inflator insertion port 34 and the mouth portion 24. However, FIG. 7 is just a schematic diagram, and in an actual device, the airbag is tightly folded multiple times with little clearance as shown in FIGS. 9(a)–9(f) to 13. Immediately after the airbag is folded (before the insertion of the inflator), the tightly folded airbag is disposed in layers on the plate-shaped portion 16a of the base plate 16. Accordingly, the top of the inflator insertion port of the base plate 16 is in a condition that the folded airbag tightly seals. In assembling the airbag device with the shape-maintaining component, the front-end side of the inflator 14 is pushed into the folded airbag through the opening 34. Therefore, the operator is required to have a significant muscle power and, in addition, it takes long time to mount the inflator.
In view of the above-mentioned problems, an object of the present invention is to provide an airbag device with an airbag shape-maintaining component, wherein an inflator is easily mounted, and an assembling efficiency is excellent.
Further objects and advantages of the invention will be apparent from the following description of the invention.